Proportional control effect in Simulink - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the proportional gain value.

Simulink

Kp = [1];

Drag options to blanks, or click blank then click option'

A5

B-3

C0

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero gain results in no control effect.

Negative gain reverses the control action.

The proportional gain Kp controls the strength of the proportional response. Setting it to 10 applies a moderate control effect.

2fill in blank

medium

Complete the code to calculate the proportional control output.

Simulink

control_output = [1] * error_signal;

Drag options to blanks, or click blank then click option'

Aerror_signal

BKp

Cintegral

Dderivative

Attempts:

3 left

💡 Hint

Common Mistakes

Multiplying error by itself instead of gain.

Using integral or derivative terms in proportional control.

The proportional control output is the product of the proportional gain Kp and the error signal.

3fill in blank

hard

Fix the error in the code to correctly update the control signal.

Simulink

control_signal = [1] + control_output;

Drag options to blanks, or click blank then click option'

Aprevious_signal

Bcontrol_output

Cerror_signal

DKp

Attempts:

3 left

💡 Hint

Common Mistakes

Adding control output to itself.

Adding error signal directly instead of control output.

The control signal is updated by adding the new control output to the previous signal value.

4fill in blank

hard

Fill both blanks to create a dictionary of control gains and their values.

Simulink

gains = [1]: [2];

Drag options to blanks, or click blank then click option'

A{'Kp', 'Ki', 'Kd'}

B{'Kp': 10, 'Ki': 0, 'Kd': 0}

C{'Kp': 5, 'Ki': 1, 'Kd': 0}

D{'Kp': 0, 'Ki': 0, 'Kd': 0}

Attempts:

3 left

💡 Hint

Common Mistakes

Using a set instead of a dictionary.

Assigning keys without values.

The dictionary gains holds the proportional, integral, and derivative gains with their values. Using the same dictionary for both blanks correctly assigns it.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension filtering gains with positive values.

Simulink

positive_gains = {k: v for k, v in gains.items() if v [1] 0 and k != [2] and k != [3]

Drag options to blanks, or click blank then click option'

A>

B<

C'Ki'

D'Kd'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for filtering positive values.

Not excluding the correct keys.

This dictionary comprehension selects gains with values greater than zero and excludes 'Ki' and 'Kd' keys.

Practice

1. What does the proportional gain (Kp) in a proportional controller primarily affect?

easy

A. The integral of the error over time

B. The delay time before the system reacts

C. The strength of the system's response to the error

D. The derivative of the error

Solution

1. Step 1: Understand the role of proportional gain

   The proportional gain (Kp) multiplies the error to determine the output response strength.

2. Step 2: Identify what Kp controls

   Kp controls how strongly the system reacts to the current error, not delay or integral/derivative terms.

3. Final Answer:

   The strength of the system's response to the error -> Option C

4. Quick Check:

   Proportional gain = response strength [OK]

Hint: Kp scales error to output strength [OK]

Common Mistakes:

• Confusing Kp with integral or derivative gains
• Thinking Kp controls delay or timing
• Mixing proportional control with PID control

2. Which of the following Simulink blocks is typically used to implement proportional control?

easy

A. Integrator block

B. Derivative block

C. Sum block

D. Gain block

Solution

1. Step 1: Identify the block that multiplies input by a constant

   The Gain block multiplies the input signal by a constant value, which is the proportional gain Kp.

2. Step 2: Match block function to proportional control

   Proportional control output = Kp * error, so Gain block is the correct choice.

3. Final Answer:

   Gain block -> Option D

4. Quick Check:

   Proportional control uses Gain block [OK]

Hint: Gain block multiplies error by Kp [OK]

Common Mistakes:

• Choosing Integrator or Derivative blocks which are for other control types
• Confusing Sum block as proportional gain
• Not knowing block functions

3. Given a proportional controller with gain Kp=3 and an error signal of 2, what is the controller output?

medium

A. 6

B. 5

C. 3

D. 2

Solution

1. Step 1: Calculate output using proportional control formula

   Output = Kp * error = 3 * 2 = 6.

2. Step 2: Verify calculation

   Multiplying gain 3 by error 2 gives 6, which matches 6.

3. Final Answer:

   6 -> Option A

4. Quick Check:

   3 * 2 = 6 [OK]

Hint: Multiply Kp by error to get output [OK]

Common Mistakes:

• Adding instead of multiplying gain and error
• Using wrong gain value
• Confusing output with error

4. A Simulink proportional controller uses a Gain block with Kp set to -4. The error signal is positive. What is the likely effect on the system output?

medium

A. Output will be zero regardless of error

B. Output will be negative, causing inverse response

C. Output will be positive, increasing error

D. Output will oscillate randomly

Solution

1. Step 1: Analyze effect of negative gain on positive error

   Output = Kp * error = -4 * positive value = negative output.

2. Step 2: Understand system response

   Negative output means control acts opposite to error, causing inverse or destabilizing response.

3. Final Answer:

   Output will be negative, causing inverse response -> Option B

4. Quick Check:

   Negative gain flips output sign [OK]

Hint: Negative Kp reverses output sign [OK]

Common Mistakes:

• Assuming output stays positive with negative gain
• Thinking output is zero without error
• Confusing oscillation with negative gain effect

5. In a Simulink model, increasing the proportional gain Kp too much causes the system to oscillate. What is the best way to reduce oscillations while keeping proportional control?

hard

A. Decrease Kp to a moderate value

B. Increase Kp further to stabilize

C. Remove the Gain block entirely

D. Set Kp to zero

Solution

1. Step 1: Understand effect of high Kp

   High Kp causes strong reactions, leading to overshoot and oscillations.

2. Step 2: Adjust Kp to reduce oscillations

   Lowering Kp reduces reaction strength, smoothing output and reducing oscillations.

3. Final Answer:

   Decrease Kp to a moderate value -> Option A

4. Quick Check:

   Lower Kp reduces oscillations [OK]

Hint: Lower Kp to smooth control [OK]

Common Mistakes:

• Increasing Kp worsens oscillations
• Removing Gain block stops control
• Setting Kp to zero disables proportional control